Polyglycolic acid polymers are known in the art and described in U.S. Pat. Nos. 3,468,853 and 3,875,937 incorporated herein by reference. Such polymers are solid, highly bioabsorbable and highly hydrolyzable. Polyglycolic acid polymers due to their ease of polymerization and other desirable characteristics are commonly spun, braided or otherwise processed into woven or nonwoven fabrics useful as surgical materials such as surgical sutures or gauze, or molded into medically useful devices such as clips or staples. High molecular weight, i.e., approximately 100,000 molecular weight or above, polyglycolic acid materials are naturally beige in color. When spun for use as sutures, the natural or beige polyglycolic acid sutures upon use become stained red with blood. The blood stained suture stitches are hardly distinguishable in tissue which can present difficulties during surgery.
In order to solve this surgical suture visibility problem, absorbable polymers are commonly colored with dyes or pigments so as to permit their distinction at first glance when in tissue, even after stained with blood. A coloring agent or pigment employed to color sutures made of an absorbable high molecular weight material such as polyglycolic acid must be nontoxic to human bodies and be absorbed by tissue and excreted. Currently, surgical sutures dyed violet, green or blue are available commercially to address this surgical suture visibility issue.
In attempting to produce polyglycolic acid suitable for the manufacture of bioabsorbable sutures, it was discovered that the customary method known in the art for producing the same in a size 65, i.e., 65 gallon, conical vortex reactor was unexpectedly unsuccessful upon changing the process over to a size 10, i.e., 10 gallon, conical vortex reactor. The customary method, typically carried out in essentially five steps, failed to produce a useful polymer. A summary of the five step process proven unsuccessful in producing useful polymer in the size 10 conical vortex reactor includes 1) distilling fresh liquid glycolide into a collection vessel maintained at 95 degrees Celsius and then charging the same into a size 65 conical vortex reactor, preheated to a temperature of 130 degrees Celsius, until half filled, 2) adding catalyst and initiator, 3) filling the remaining unfilled half of the reactor with glycolide, 4) heating the reactor until the glycolide reaches a uniform temperature of 135 degrees Celsius, and 5) increasing the reactor temperature at one degree Celsius intervals, i.e., "ramping", until the "glycolide" reaches a uniform temperature of 220 degrees Celsius.
As described above, the conventional, known process for producing polyglycolic acid polymer in a size 65 conical vortex reactor is unsatisfactory for producing the same polymer using a size 10 conical vortex reactor.